1. Field of the Invention
This invention relates generally to telecommunications, and, more particularly, to wireless communications.
2. Description of the Related Art
In the field of wireless telecommunications, such as cellular telephony, a system typically includes a plurality of base stations distributed within an area to be serviced by the system. Various users within the area, fixed or mobile, may then access the system and, thus, other interconnected telecommunications systems, via a wireless link with one or more of the base stations. Typically, a mobile device maintains communications with the system as the mobile device passes through an area by communicating with one and then another base station, as the user moves. The mobile device may communicate with the closest base station, the base station with the strongest signal, the base station with a capacity sufficient to accept communications, etc.
Generally, voice and data may be transmitted over the wireless link using two basic switching technologies. Traditional voice telephone calls, as well as data provided by a modem, are transmitted using a circuit-switched connection. Alternatively, voice and data may be transmitted over a packet-switched network using a Voice over Internet Protocol (often referred to as VoIP). Both the circuit-switched and the packet-switched networks may include wired and/or wireless connections. The Voice over Internet Protocol is increasingly common, at least in part because VoIP can handle voice and data communications homogeneously. Moreover, transmitting voice with VoIP may help reduce operational costs. In addition to conventional land-line telephones and cellular telephones, VoIP may be used to incorporate voice communications in devices such as personal data assistants, laptop computers, desktop computers, and the like.
The mobility of these devices introduces an element of variability regarding their location at any given time. Those skilled in the art will appreciate that the location of an emergency E911 call originating from such a mobile device may be highly useful to insure that assistance arrives in a timely fashion. For example, emergency calls are currently directed to an “appropriate” Public Safety Answering Point (PSAP) associated with the location from which an emergency call originates. A PSAP is a facility that is equipped and staffed on a 24-hour basis to receive and process emergency E911 calls. Generally, the phone number for each device on a fixed or land line network capable of initiating an E911 call has an appropriate PSAP associated with it to receive that E911 call. This is because land line telephone numbers are assigned geographically. However, owing to the mobility of devices, such as cell phones, personal data assistants (PDAs), laptop computers, and the like, the appropriate PSAP may vary, depending upon the current location of the mobile device, not the geographic location to which the number would belong if assigned to a non-mobile device.